Lightweight collapsible structures useful for a variety of purposes have been disclosed in a number of U.S. patents and Canadian patents exemplified by the following:
U.S. Pat. No. 433,635 issued August 1890; PA1 U.S. Pat. No. 844,066 issued February 1907; PA1 U.S. Pat. No. 1,875,460 issued September 1932; PA1 U.S. Pat. No. Re. 21,371 issued February 1940; PA1 U.S. Pat. No. 2,587,316 issued February 1952; PA1 Canadian Pat. No. 312,291 issued June 1931; PA1 Canadian Pat. No. 315,615 issued Sept. 29, 1931; PA1 Canadian Pat. No. 641,733 issued May 1962.
This invention relates to improvements in such collapsible structures but particularly of the nature disclosed in my U.S. Pat. No. 3,990,669 which issued Nov. 9, 1976 and the Canadian counterpart, Canadian Pat. No. 1,010,008 issued May 10, 1977.